A test device and test method for shield cutterhead mud cake considering high temperature and high pressure

Abstract

The present invention provides a test device for shield cutterhead mud cakes taking into account high temperature and high pressure. A double-layer cylindrical test cylinder is sealed at the bottom by a cylindrical cylinder bottom cover (4). The top of the double-layer cylindrical test cylinder is open. A cylindrical inner cylinder top cover (3) is movably arranged at the top opening. An electric-controlled jack (5) for applying vertical pressure is connected to the upper surface of the cylindrical inner cylinder top cover (3). A plurality of electrically controllable heating rods (13), a plurality of unconfined compressive strength sample molds (11) and a plurality of direct shear sample molds (12) are arranged inside the double-layer cylindrical test cylinder. The present invention also discloses a test method for shield cutterhead mud cakes taking into account high temperature and high pressure. The present invention can study the mechanism or conditions of cutterhead mud cakes under the action of high temperature and high pressure, which is more consistent with the actual situation and avoids the operation of injecting a dispersant to decompose the mud cakes after the mud cakes are formed in shield practice.

Description

Technical Field

[0001] The invention relates to a test device and a test method for shield cutter head mud cake considering high temperature and high pressure, belonging to the technical field of underground engineering test and testing. Background Art

[0002] Earth pressure shield technology has become the mainstream construction method for urban tunnel construction in my country. Earth pressure shield construction has the advantages of minimizing the impact on the surrounding environment, being unaffected by weather during construction, and having little impact on road traffic, and has been widely used in my country. However, my country has a vast territory and complex and changeable geological conditions. From hard plastic clay layers, silty silty clay layers, fine silt sand layers, medium coarse sand layers, and pebble layers to surrounding rock layers of various weathering degrees, shield technology has to adapt to various geological conditions, and a series of problems have also arisen. Among them, when encountering clay layers such as hard plastic clay and red layers with high clay content, mud cakes will be inevitable, which has become a difficult problem that has been difficult to cure in shield construction for many years.

[0003] When the cutterhead of an earth pressure shield excavates underground, it generates a lot of heat by friction with the soil. When the water content of the soil itself is low, the clay in the soil will undergo pressure consolidation and cementation, causing the excavated soil to adhere to the cutterhead and the cutter. The frequent failure of mud cake formation causes the earth pressure shield to frequently shut down and open the cabin to use a pneumatic pick to knock off the mud cake on the cutterhead during excavation. This not only increases the risk during the excavation of the earth pressure shield, but also greatly reduces the excavation efficiency of the earth pressure shield. The formation of mud cake on the cutterhead of the earth pressure shield has become an insurmountable "threshold" in the development of shield technology so far. The root of the problem is that there is no high temperature and high pressure test equipment on the market at present, and there are many difficulties in design and implementation. It is necessary to integrate knowledge in multiple disciplines such as soil mechanics, electromagnetics, thermodynamics, and seepage to overcome the difficulties of this test.

[0004] Since the formation mechanism of mud cake is not very clear at present, and it involves the combined influence of formation, pressure and temperature, it is difficult to carry out the current experiment. Therefore, the current research is more of a summary of engineering experience, which is a qualitative conclusion. It lacks experimental data guidance and is difficult to form a theoretical system. It has become an insurmountable problem for the advancement of shield technology. It is urgent to carry out the research and development of experimental technology and experimental equipment to provide important data support for the research on the problem of shield mud cake.

[0005] In the existing construction, there are many ways to deal with the problem of mud cake on the cutter disc, but the efficiency is not high and the construction period is long. For the general situation where the mud cake is not serious, the main method is to inject foaming agent, dispersant and other liquids to soak the cutter disc with mud cake for 1-2 days to gradually peel it off, and then rotate the cutter disc at high speed to centrifuge the mud cake off. For the serious mud cake, workers need to enter the warehouse with pressure to knock and pick the mud cake on the cutter disc. In addition, entering the warehouse with pressure requires more preparatory work, such as preparing mud, injecting pressure chamber to replace the cabin soil, making mud film, and then lowering the liquid level of the mud and water chamber. Workers enter the warehouse with pressure and use hydraulic picks, pneumatic picks and other tools to break and clean the mud cake, facing the risk of collapse of the shield excavation face; for extremely unstable strata, the foundation of the excavation face needs to be reinforced to reduce the risk of collapse of the excavation face when the cabin is opened with pressure to break the mud cake.

[0006] In fact, there are strata with mud cakes in the project, and there is also the possibility of eruption, and the two are often accompanied by each other. For example, in the fractured weathered rock strata with high mud content, there is abundant underground fissure water, and the rock samples cut down absorb a small amount of water and become extremely viscous soil. Since shield tunneling is carried out in this stratum, half-cabin under-pressure construction is generally implemented, and the soil samples enter the pressure cabin and are quickly discharged, with almost no sufficient time for uniform mixing, resulting in mud cakes and eruptions. These two construction failures are almost accompanied by each other, causing great difficulties to the construction.

[0007] When shield tunneling in strata prone to mud cake formation, what is needed is the ability to accurately identify and prevent it in real time.

[0008] The present invention proposes a new law of change of soil strength properties under the combined effects of pressure and temperature, which can consider pressure alone, temperature alone, or pressure and temperature together, and based on the actual situation of shield engineering, gives reasonable suggestions for slag improvement and conditions for distinguishing mud cakes, so as to ensure the safety of excavation and the efficiency and economy of shield cutting. Summary of the invention

[0009] The technical problem to be solved by the present invention is to provide a test device for shield cutter head mud cake taking into account high temperature and high pressure. The device is used to study the occurrence mechanism and conditions of mud cake of clay or mudstone, which provides important guidance and reference for selecting suitable types of improvers and economical addition amounts for shield excavation in clay or mudstone strata.

[0010] At the same time, the present invention provides a test method for shield cutter head mud cake taking into account high temperature and high pressure. The method takes into account the changing law of soil strength properties under the combined action of pressure and temperature, and can accurately identify and prevent the occurrence of mud cake phenomenon during shield excavation in real time.

[0011] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0012] A test device for shield cutter head mud cake taking into account high temperature and high pressure comprises a double-layer cylindrical test cylinder, the bottom of the double-layer cylindrical test cylinder is sealed by a cylindrical cylinder bottom cover, the top of the double-layer cylindrical test cylinder is open, a cylindrical inner cylinder top cover is movably arranged at the top opening, an electric-controlled jack for applying vertical pressure is connected to the upper surface of the cylindrical inner cylinder top cover, a plurality of electrically controllable heating rods, a plurality of unconfined compressive strength specimen molds and a plurality of direct shear specimen molds are arranged in the double-layer cylindrical test cylinder.

[0013] The electrically controllable heating rod is connected to a controller; the electrically controllable heating rod, the controller and the electrically controlled jack are all powered by a power supply.

[0014] The double-layer cylindrical test cylinder comprises a cylindrical outer cylinder and a cylindrical inner cylinder. The upper surface of the cylindrical cylinder bottom cover is provided with two concentric circle-shaped grooves 1 for inserting the bottom end of the cylindrical outer cylinder and groove 2 for inserting the bottom end of the cylindrical inner cylinder; the top end of the cylindrical outer cylinder and the top end of the cylindrical inner cylinder are sealed and connected.

[0015] Four vertically arranged reaction frame vertical rods are evenly distributed on the cylindrical bottom cover located outside the groove, and the top ends of the reaction frame vertical rods are integrally connected with threaded rods, and the diameter of the threaded rods is smaller than the diameter of the reaction frame vertical rods. The top end of the electric jack is connected to the center of the reaction frame cross, and the ends of the reaction frame crosses are provided with through holes for penetrating the threaded rods, and the diameter of the through holes is smaller than the diameter of the reaction frame vertical rods. After the reaction frame cross passes through the through holes, it is fastened by a reaction frame nut.

[0016] The electric controlled jack comprises a shell and a telescopic head located at the bottom end of the shell, the top end of the shell is connected to the reaction frame cross, and the bottom end of the telescopic head is connected to the upper surface of the cylindrical inner tube top cover.

[0017] The unconfined compressive strength specimen mold is a cylindrical tube with openings at the top and bottom.

[0018] The direct shear specimen mold is a double-layer direct shear specimen mold, and the double-layer direct shear specimen mold comprises a metal block below the bottom layer and a ring knife integrally connected to the top of the metal block.

[0019] The material of the metal block includes aluminum or iron.

[0020] A test method for shield cutterhead mud cake considering high temperature and high pressure, comprising the following steps:

[0021] Step 1: Insert the double-layer cylindrical test cylinder into the grooves 1 and 2 of the bottom cover of the cylindrical cylinder, evenly place the unconfined compressive strength specimen mold and the direct shear specimen mold filled with soil samples inside the double-layer cylindrical test cylinder, and use the soil sample to fill other blank areas and compact them until the soil sample is 2-3 cm higher than the top of the mold and compact them; at the same time, evenly insert the powered controllable heating rod into the soil layer;

[0022] Step 2: Pass the reaction frame cross through the threaded rod at the top of the reaction frame vertical rod, so that the top cover of the cylindrical inner tube contacts the upper surface of the soil layer, and then install the reaction frame nut on the upper surface of the reaction frame cross and tighten it; the electric jack applies vertical pressure to the soil layer to a certain set value and maintains it;

[0023] Step 3: Power on the electrically controllable heating rod and set it to a set temperature;

[0024] Step 4: The test continues until a certain set time;

[0025] Step 5: After power off and pressure relief, open the top cover of the cylindrical inner tube, take out the unconfined compressive strength specimen mold and the direct shear specimen mold placed in the double-layer cylindrical test tube, demould them, and then carry out unconfined compressive strength and direct shear strength tests respectively;

[0026] Step 6: Determine the probability and conditions of mud cake formation on the shield cutter head based on the unconfined compressive strength and direct shear strength;

[0027] Step 7: Improve the soil sample and repeat steps 1 to 6 until the appropriate soil conditioner and its dosage are determined.

[0028] In step seven, the suitable soil conditioner is mainly clay dispersant, water or foam.

[0029] In the present invention, the unconfined compressive strength specimen mold and the direct shear specimen mold can be directly placed in the cylinder without being fixed; the electrically controllable heating rod can be fixed on the bottom cover of the cylindrical inner cylinder, and the control line of the electrically controllable heating rod passes through the bottom cover of the cylindrical inner cylinder and is connected to the controller.

[0030] Beneficial effects of the present invention: Compared with the prior art, the present invention provides a test device and test method for shield cutter head mud cake taking into account high temperature and high pressure, which can study the mechanism or conditions of cutter head tool mud cake formation under high temperature and high pressure (the probability and conditions of mud cake formation are mainly determined by comprehensive comparative analysis of the unconfined compressive strength of soil samples under high temperature and high pressure conditions and the direct shear strength of the soil sample and the metal interface), which is more in line with the actual situation and avoids the operation of injecting dispersant to decompose the mud cake after the mud cake is formed in shield practice.

[0031] Through practical verification, the test device of the present invention can better carry out mud cake experiments on clay soils, and has the characteristics of simple operation, high efficiency, convenient installation and disassembly of the equipment, and convenient sampling.

[0032] (1) The present invention takes into account the high temperature and high pressure conditions of mud cake formation, sets the corresponding temperature and pressure, and keeps them unchanged.

[0033] (2) The present invention takes into account the problem of sampling after mud cake formation, which is very convenient for conducting unconfined compressive strength and direct shear strength tests of soil samples after mud cake formation.

[0034] (3) The present invention proposes an unconfined compressive strength index for quantitatively evaluating whether a mud cake is formed and the degree of formation.

[0035] (4) The experimental results obtained by the test device of the present invention can summarize the conditions for the formation of mud cakes in various clay layers, such as the pressure at which mud cakes are more likely to form and the temperature at which mud cakes are more likely to form. It is also possible to propose the feasibility and effectiveness of reducing the formation of mud cakes by adding water, dispersants, etc. according to the actual conditions of the project.

[0036] (5) The present invention was successfully applied in the Guangzhou Metro strata. By adding a 1% concentration of dispersant produced by Dongguan Mingjie Tunnel Construction Materials Co., Ltd. into the foaming agent, the probability of mud cake on the shield cutter head was greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of the structure of the present invention;

[0038] Figure 2 It is a schematic structural diagram of the cylindrical bottom cover of the present invention;

[0039] Figure 3 yes Figure 1 Cross-sectional diagram;

[0040] Figure 4 It is a structural schematic diagram of the direct shearing specimen mold in the present invention;

[0041] Figure 5 It is a structural schematic diagram of the unconfined compressive strength specimen mold in the present invention. DETAILED DESCRIPTION

[0042] The following is a further detailed description of a test device and a test method for shield cutterhead mud cake considering high temperature and high pressure of the present invention in conjunction with the accompanying drawings and specific embodiments.

[0043] Example 1

[0044] like Figure 1As shown, a test device for shield cutter head mud cake considering high temperature and high pressure includes a double-layer cylindrical test cylinder, the double-layer cylindrical test cylinder includes a cylindrical outer cylinder 1 and a cylindrical inner cylinder 2, the double-layer cylindrical test cylinder is closed at the bottom and opened at the top through a cylindrical cylinder bottom cover 4, the top opening is connected to an electric control jack 5 and a cylindrical inner cylinder top cover 3, the electric control jack 5 can apply vertical pressure, the cylindrical inner cylinder 2 is a metal cylinder, and the cylindrical outer cylinder 1 is a ceramic cylinder.

[0045] like Figure 3 As shown, a plurality of electrically controllable heating rods 13 and a plurality of unconfined compressive strength specimen molds 11 and direct shear specimen molds 12 are arranged in the double-layer cylindrical test tube; the electrically controllable heating rods 13 are set at a certain temperature and maintained through a temperature control module.

[0046] The electrically controllable heating rod 13 is connected to a controller; the electrically controllable heating rod 13, the controller and the electrically controlled jack 5 are all powered by a power supply.

[0047] like Figure 2 As shown, the upper surface of the cylindrical bottom cover 4 is provided with two concentric grooves 1 9 for inserting the bottom end of the cylindrical outer cylinder 1 and a groove 2 10 for inserting the bottom end of the cylindrical inner cylinder 2; the top end of the cylindrical outer cylinder 1 and the top end of the cylindrical inner cylinder 2 are sealed and connected.

[0048] Four vertically arranged reaction frame vertical rods 6 are evenly distributed on the cylindrical bottom cover 4 located outside the groove 9, and the top of the reaction frame vertical rod 6 is integrally connected with a threaded rod, and the diameter of the threaded rod is smaller than the diameter of the reaction frame vertical rod 6. The top of the electric jack 5 is connected to the center of the reaction frame cross 7, and the end of the reaction frame cross 7 is provided with a through hole for passing through the threaded rod, and the diameter of the through hole is smaller than the diameter of the reaction frame vertical rod 6. After the reaction frame cross 7 passes through the through hole, it is fastened by the reaction frame nut 8.

[0049] The electric jack 5 includes a shell and a telescopic head located at the bottom end of the shell, the top end of the shell is connected to the reaction frame cross 7, and the bottom end of the telescopic head is connected to the upper surface of the cylindrical inner tube top cover 3.

[0050] like Figure 5 As shown, the unconfined compressive strength specimen mold 11 is a cylindrical tube 16 with openings at the top and bottom.

[0051] like Figure 4 As shown, the direct shear specimen mold 12 is a double-layer direct shear specimen mold, and the double-layer direct shear specimen mold includes a metal block 14 below the bottom layer and a ring knife 15 integrally connected to the top of the metal block 14 .

[0052] The metal block 14 is made of aluminum or iron.

[0053] Example 2

[0054] like Figure 1~Figure 5 As shown, a test method for shield cutterhead mud cake considering high temperature and high pressure includes the following steps:

[0055] Step 1: insert the double-layer cylindrical test cylinder into the groove 1 9 and the groove 2 10 of the cylindrical cylinder bottom cover 4, evenly place the unconfined compressive strength sample mold 11 and the direct shear sample mold 12 filled with soil samples inside the double-layer cylindrical test cylinder, and use the soil sample to fill other blank areas and compact them until the soil sample is 2-3 cm higher than the top of the mold and compact them; at the same time, evenly insert the powered controllable heating rod 13 into the soil layer;

[0056] Step 2: Pass the reaction frame cross 7 through the threaded rod at the top of the reaction frame vertical rod 6, so that the cylindrical inner tube top cover 3 contacts the upper surface of the soil layer, and then install the reaction frame nut 8 on the upper surface of the reaction frame cross 7 and tighten it; the electric control jack 5 applies vertical pressure to the soil layer to a certain set value and maintains it;

[0057] Step 3: Power on the controllable heating rod 13 and set it to a certain set temperature;

[0058] Step 4: The test continues until a certain set time;

[0059] Step 5: After power off and pressure relief, open the top cover 3 of the cylindrical inner tube, take out the unconfined compressive strength specimen mold 11 and the direct shear specimen mold 12 placed in the double-layer cylindrical test tube, demould them, and then carry out unconfined compressive strength and direct shear strength tests respectively;

[0060] Step 6: Determine the probability and conditions of mud cake formation on the shield cutter head based on the unconfined compressive strength and direct shear strength;

[0061] Step 7: Improve the soil sample and repeat steps 1 to 6 until the appropriate soil conditioner and its dosage are determined.

[0062] In step six, the probability and conditions of the occurrence of mud cake are mainly determined by comprehensive comparative analysis of the unconfined compressive strength of the soil sample under high temperature and high pressure conditions and the direct shear strength of the soil sample and metal interface.

[0063] In step seven, the suitable soil conditioner is mainly clay dispersant, water or foam.

[0064] The present invention aims to solve the inefficient practice that the mechanism and conditions of mud cake formation in earth pressure shield structures are not clear in current projects, and the only way is to carry out continuous trial mixing on site to improve the slag or inject dispersants into the pressure chamber to peel off the mud cake after the mud cake is formed. To this end, the present invention establishes a test device for mud cake formation on the cutter head of a shield structure taking into account high temperature and high pressure, and conducts research on the mechanism and conditions of mud cake formation in clay or mudstone, which provides important guidance and reference for selecting the appropriate type of improver and the economic amount of addition for shield excavation in clay or mudstone formation.

[0065] In the description provided herein, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

[0066] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by the terms "up", "down", "front", "back", "left", "right", etc. are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0067] Similarly, it should be understood that in order to streamline the present disclosure and aid in understanding one or more of the various inventive aspects, in the above description of exemplary embodiments of the present invention, various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, this disclosed method should not be interpreted as reflecting the intention that the claimed invention requires more features than those expressly recited in each claim. Rather, as reflected in the claims, inventive aspects lie in less than all of the features of the individual embodiments previously disclosed. Therefore, the claims that follow the detailed description are hereby expressly incorporated into the detailed description, with each claim itself serving as a separate embodiment of the present invention.

[0068] As used herein, unless otherwise specified, the use of ordinal numbers "first," "second," "third," etc. to describe common objects merely indicates that different instances of similar objects are involved, and is not intended to imply that the objects so described must have a given order in time, space, order, or in any other manner.

[0069] Although the present invention has been described according to a limited number of embodiments, it will be apparent to those skilled in the art, with the benefit of the above description, that other embodiments may be envisioned within the scope of the invention thus described. In addition, it should be noted that the language used in this specification is selected primarily for readability and teaching purposes, rather than for explaining or defining the subject matter of the present invention. Therefore, many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the present invention is illustrative, not restrictive, with respect to the scope of the present invention, which is defined by the appended claims.

[0070] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A test device for shield cutterhead mud cake considering high temperature and high pressure, characterized in that: The double-layer cylindrical test cylinder comprises a double-layer cylindrical test cylinder, wherein the double-layer cylindrical test cylinder is sealed at the bottom by a cylindrical cylinder bottom cover (4), the top of the double-layer cylindrical test cylinder is open, a cylindrical inner cylinder top cover (3) is movably arranged at the top opening, an electric-controlled jack (5) for applying vertical pressure is connected to the upper surface of the cylindrical inner cylinder top cover (3), and a plurality of electrically controllable heating rods (13), a plurality of unconfined compressive strength specimen molds (11), and a plurality of direct shear specimen molds (12) are arranged inside the double-layer cylindrical test cylinder.

2. A test device for shield cutterhead mud cake considering high temperature and high pressure according to claim 1, characterized in that: The electrically controllable heating rod (13) is connected to a controller; the electrically controllable heating rod (13), the controller and the electrically controlled jack (5) are all powered by a power supply.

3. A test device for shield cutterhead mud cake considering high temperature and high pressure according to claim 1, characterized in that: The double-layer cylindrical test cylinder comprises a cylindrical outer cylinder (1) and a cylindrical inner cylinder (2); the upper surface of the cylindrical cylinder bottom cover (4) is provided with two concentric circle-shaped grooves 1 (9) for inserting the bottom end of the cylindrical outer cylinder (1) and groove 2 (10) for inserting the bottom end of the cylindrical inner cylinder (2); the top end of the cylindrical outer cylinder (1) and the top end of the cylindrical inner cylinder (2) are sealed and connected.

4. A test device for shield cutterhead mud cake considering high temperature and high pressure according to claim 3, characterized in that: Four vertically arranged reaction frame vertical rods (6) are evenly distributed on the cylindrical bottom cover (4) located outside the groove 1 (9), and the top of the reaction frame vertical rod (6) is integrally connected with a threaded rod, and the diameter of the threaded rod is smaller than the diameter of the reaction frame vertical rod (6). The top of the electric control jack (5) is connected to the center of the reaction frame cross (7), and the end of the reaction frame cross (7) is provided with a through hole for penetrating the threaded rod, and the diameter of the through hole is smaller than the diameter of the reaction frame vertical rod (6). After the reaction frame cross (7) passes through the through hole, it is fastened by a reaction frame nut (8).

5. A test device for shield cutterhead mud cake considering high temperature and high pressure according to claim 4, characterized in that: The electric-controlled jack (5) comprises a shell and a telescopic head located at the bottom end of the shell, the top end of the shell is connected to the reaction frame cross (7), and the bottom end of the telescopic head is connected to the upper surface of the cylindrical inner tube top cover (3).

6. The test device for shield cutterhead mud cake considering high temperature and high pressure according to claim 1 is characterized in that: The unconfined compressive strength specimen mold (11) is a cylindrical tube (16) that is open at the top and bottom.

7. The test device for shield cutterhead mud cake considering high temperature and high pressure according to claim 1 is characterized in that: The direct shear specimen mold (12) is a double-layer direct shear specimen mold, comprising a metal block (14) below a bottom layer and a ring knife (15) integrally connected to the top of the metal block (14).

8. The test device for shield cutterhead mud cake considering high temperature and high pressure according to claim 7, characterized in that: The material of the metal block (14) includes aluminum or iron.

9. A test method for shield cutterhead mud cake considering high temperature and high pressure, characterized in that: The test method adopts a test device for shield cutter head mud cake that takes into account high temperature and high pressure, comprising a double-layer cylindrical test cylinder, the double-layer cylindrical test cylinder is sealed at the bottom by a cylindrical cylinder bottom cover (4), the top of the double-layer cylindrical test cylinder is open, a cylindrical inner cylinder top cover (3) is movably arranged at the top opening, the upper surface of the cylindrical inner cylinder top cover (3) is connected to an electric control jack (5) for applying vertical pressure, and a plurality of electrically controllable heating rods (13), a plurality of unconfined compressive strength specimen molds (11) and a plurality of direct shear specimen molds (12) are arranged inside the double-layer cylindrical test cylinder; The double-layer cylindrical test cylinder comprises a cylindrical outer cylinder (1) and a cylindrical inner cylinder (2); the upper surface of the cylindrical cylinder bottom cover (4) is provided with two concentric circle-shaped grooves 1 (9) for inserting the bottom end of the cylindrical outer cylinder (1) and groove 2 (10) for inserting the bottom end of the cylindrical inner cylinder (2); the top end of the cylindrical outer cylinder (1) and the top end of the cylindrical inner cylinder (2) are sealed and connected; Four vertically arranged reaction frame vertical rods (6) are evenly distributed on the cylindrical bottom cover (4) located outside the groove 1 (9), the top end of the reaction frame vertical rod (6) is integrally connected with a threaded rod, the diameter of the threaded rod is smaller than the diameter of the reaction frame vertical rod (6), the top end of the electric control jack (5) is connected to the center of the reaction frame cross (7), the end of the reaction frame cross (7) is provided with a through hole for penetrating the threaded rod, the diameter of the through hole is smaller than the diameter of the reaction frame vertical rod (6), and the reaction frame cross (7) is fastened by a reaction frame nut (8) after passing through the through hole; The test method comprises the following steps: Step 1: insert the double-layer cylindrical test tube into the groove 1 (9) and groove 2 (10) of the bottom cover (4) of the cylindrical tube, evenly place the unconfined compressive strength specimen mold (11) and the direct shear specimen mold (12) filled with soil samples inside the double-layer cylindrical test tube, and fill other blank areas with soil samples and compact them until the soil samples are 2-3 cm higher than the top of the molds and compact them; at the same time, evenly insert the powered controllable heating rod (13) into the soil layer; Step 2: Pass the reaction frame cross (7) through the threaded rod at the top of the reaction frame vertical rod (6) so that the cylindrical inner tube top cover (3) contacts the upper surface of the soil layer, and then install the reaction frame nut (8) on the upper surface of the reaction frame cross (7) and tighten it; the electric control jack (5) applies vertical pressure to the soil layer to a certain set value and maintains it; Step 3: Power on the electrically controllable heating rod (13) and set it to a set temperature; Step 4: The test continues until a certain set time; Step 5: After power is turned off and pressure is released, the top cover (3) of the cylindrical inner tube is opened, and the unconfined compressive strength specimen mold (11) and the direct shear specimen mold (12) placed in the double-layer cylindrical test tube are taken out and demoulded, and then the unconfined compressive strength and direct shear strength tests are respectively carried out; Step 6: Determine the probability and conditions of mud cake formation on the shield cutter head based on the unconfined compressive strength and direct shear strength; Step 7: Improve the soil sample and repeat steps 1 to 6 until the appropriate slag conditioner and its addition amount are determined.

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